Asurvey is planned to determine the mean annual family medical expenses of employees of a large company. the management of the company wishes to be 90% confident that the sample mean is correct to within plus or minus$40 of the population mean annual family medical expenses. a previous study indicates that the standard deviation is approximately $341. a. how large a sample is necessary?

b. if management wants to be correct to within (plus or minus $25), how many employees need to be selected?